When we finally get a glimpse at that “thing” growing inside of Duncan Haslip (Ken Marino of TV’s “Children’s Hospital”), we understand the hour-long trips to the toilet, accompanied by screaming. It’s big, bald and wrinkled — E.T. with teeth and claws.

His doctor (Toby Huss) was re-assuring. “You’ve got a thing in your butt,” and it’s due to “poor stress management.” All Duncan had to do was dial down the stress and all would be well.

But he works for a creep (Patrick Warburton) who has moved him into human resources, where Duncan is now in charge of layoffs at his investment firm. The boss thinks it’s cute to slip inappropriate articles into the “packets” each laid off worker receives — condoms, for instance.

And then there’s the nutjob, played by an inspired Peter Stormare (“Fargo”) who becomes Duncan’s stress therapist. This quack’s parrot is always blurting out deep truths in the middle of their sessions.

“Witch doctor! Witch doctor!”

Then the polyp pops loose. “Milo,” Duncan calls him, because his therapist thinks he should bond with it. If not, Milo will kill everybody who stresses Duncan. And we wouldn’t want that.

The random laughs aren’t plentiful enough to justify the endless loop of poop puns that “Bad Milo!” serves up. Marino is pretty good at showing a working man at the end of his tether — and his colon.

The production helps him, here and there. Duncan’s so stressed he can’t sleep, can’t please anyone or take care of even the simplest chores. I giggled at the “Wash me” scrawled on the dirt of his driver’s side car window.

It’s fitfully amusing, as bowel movement comedies go. But “Bad Milo!” is the sort of film that you’ll want to watch at midnight, even after it’s migrated from cinemas to home video. At that hour of the night, in the right frame of mind, most anything’ll flush.

MPAA Rating: R for bloody comic horror violence, and for language and some sexual content